/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 2001-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: Expression.java,v 1.2.4.1 2005/09/01 14:17:51 pvedula Exp $
 */

package com.sun.org.apache.xalan.internal.xsltc.compiler;

import java.util.Vector;

import com.sun.org.apache.bcel.internal.generic.BranchHandle;
import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
import com.sun.org.apache.bcel.internal.generic.GOTO_W;
import com.sun.org.apache.bcel.internal.generic.IFEQ;
import com.sun.org.apache.bcel.internal.generic.InstructionHandle;
import com.sun.org.apache.bcel.internal.generic.InstructionList;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.BooleanType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ErrorMsg;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.NodeSetType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypeCheckError;

/**
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 * @author Morten Jorgensen
 * @author Erwin Bolwidt <ejb@klomp.org>
 */
abstract class Expression extends SyntaxTreeNode {

  /**
   * The type of this expression. It is set after calling
   * <code>typeCheck()</code>.
   */
  protected Type _type;

  /**
   * Instruction handles that comprise the true list.
   */
  protected FlowList _trueList = new FlowList();

  /**
   * Instruction handles that comprise the false list.
   */
  protected FlowList _falseList = new FlowList();

  public Type getType() {
    return _type;
  }

  public abstract String toString();

  public boolean hasPositionCall() {
    return false;           // default should be 'false' for StepPattern
  }

  public boolean hasLastCall() {
    return false;
  }

  /**
   * Returns an object representing the compile-time evaluation
   * of an expression. We are only using this for function-available
   * and element-available at this time.
   */
  public Object evaluateAtCompileTime() {
    return null;
  }

  /**
   * Type check all the children of this node.
   */
  public Type typeCheck(SymbolTable stable) throws TypeCheckError {
    return typeCheckContents(stable);
  }

  /**
   * Translate this node into JVM bytecodes.
   */
  public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
    ErrorMsg msg = new ErrorMsg(ErrorMsg.NOT_IMPLEMENTED_ERR,
        getClass(), this);
    getParser().reportError(FATAL, msg);
  }

  /**
   * Translate this node into a fresh instruction list.
   * The original instruction list is saved and restored.
   */
  public final InstructionList compile(ClassGenerator classGen,
      MethodGenerator methodGen) {
    final InstructionList result, save = methodGen.getInstructionList();
    methodGen.setInstructionList(result = new InstructionList());
    translate(classGen, methodGen);
    methodGen.setInstructionList(save);
    return result;
  }

  /**
   * Redefined by expressions of type boolean that use flow lists.
   */
  public void translateDesynthesized(ClassGenerator classGen,
      MethodGenerator methodGen) {
    translate(classGen, methodGen);
    if (_type instanceof BooleanType) {
      desynthesize(classGen, methodGen);
    }
  }

  /**
   * If this expression is of type node-set and it is not a variable
   * reference, then call setStartNode() passing the context node.
   */
  public void startIterator(ClassGenerator classGen,
      MethodGenerator methodGen) {
    // Ignore if type is not node-set
    if (_type instanceof NodeSetType == false) {
      return;
    }

    // setStartNode() should not be called if expr is a variable ref
    Expression expr = this;
    if (expr instanceof CastExpr) {
      expr = ((CastExpr) expr).getExpr();
    }
    if (expr instanceof VariableRefBase == false) {
      final InstructionList il = methodGen.getInstructionList();
      il.append(methodGen.loadContextNode());
      il.append(methodGen.setStartNode());
    }
  }

  /**
   * Synthesize a boolean expression, i.e., either push a 0 or 1 onto the
   * operand stack for the next statement to succeed. Returns the handle
   * of the instruction to be backpatched.
   */
  public void synthesize(ClassGenerator classGen, MethodGenerator methodGen) {
    final ConstantPoolGen cpg = classGen.getConstantPool();
    final InstructionList il = methodGen.getInstructionList();
    _trueList.backPatch(il.append(ICONST_1));
    final BranchHandle truec = il.append(new GOTO_W(null));
    _falseList.backPatch(il.append(ICONST_0));
    truec.setTarget(il.append(NOP));
  }

  public void desynthesize(ClassGenerator classGen,
      MethodGenerator methodGen) {
    final InstructionList il = methodGen.getInstructionList();
    _falseList.add(il.append(new IFEQ(null)));
  }

  public FlowList getFalseList() {
    return _falseList;
  }

  public FlowList getTrueList() {
    return _trueList;
  }

  public void backPatchFalseList(InstructionHandle ih) {
    _falseList.backPatch(ih);
  }

  public void backPatchTrueList(InstructionHandle ih) {
    _trueList.backPatch(ih);
  }

  /**
   * Search for a primop in the symbol table that matches the method type
   * <code>ctype</code>. Two methods match if they have the same arity.
   * If a primop is overloaded then the "closest match" is returned. The
   * first entry in the vector of primops that has the right arity is
   * considered to be the default one.
   */
  public MethodType lookupPrimop(SymbolTable stable, String op,
      MethodType ctype) {
    MethodType result = null;
    final Vector primop = stable.lookupPrimop(op);
    if (primop != null) {
      final int n = primop.size();
      int minDistance = Integer.MAX_VALUE;
      for (int i = 0; i < n; i++) {
        final MethodType ptype = (MethodType) primop.elementAt(i);
        // Skip if different arity
        if (ptype.argsCount() != ctype.argsCount()) {
          continue;
        }

        // The first method with the right arity is the default
        if (result == null) {
          result = ptype;             // default method
        }

        // Check if better than last one found
        final int distance = ctype.distanceTo(ptype);
        if (distance < minDistance) {
          minDistance = distance;
          result = ptype;
        }
      }
    }
    return result;
  }
}
